Method of processing oil shale

ABSTRACT

THE PRESENT INVENTION COMPRISES A METHOD OF ECOMOMICALLY PROCESSING OIL SHALE AT LOW TEMPERATURES AND PRESSURES IN SUCH A MANNER THAT THE EFFECTIVE YIELD OF END PRODUCTS FROM KEROGEN IN THE SHALE IS MEASURABLY INCREASED, AND AT REDUCED COST, OVER THAT POSSIBLE BY THE EMPLOYMENT OF CONVENTIONAL METHODS. IN THE PRESENT INVENTION, THE PROCESS EMPLOYS THE TWIN STEPS OF, FIRST, SOAKING CRUSHED OIL SHALE IN A LIQUID, HYDROCARBON DILUENT, AND THEN, AFTER THE SOAKING HAS BEEN COMPLETED, SUBJECTING THE SHALE-DILUENT MIXTURE TO HEAT TO GRADUALLY INCREASE MIXTURE TEMPERATURE   FROM AMBIENT CONDITION, SO AS TO ENABLE MAXIMUM RECOVERY ULTIMATLEY, OF DISTILLATES. THE DUAL FUNCTIONS OF, FIRST, SOAKING THE OIL SHALE IN A DILUENT UNDER AMBIENT TEMPERATURE CONDITIONS AND, SECONDLY, GRADUALLY AND PROGRESSIVELY INCREASING THE TEMPERATURE OF THE SHALE, HAS BEEN FOUND TO INCREASE MEASURABLY THE YIELD OF PRODUCTS VAPORIZED FROM THE KEROGEN OF THE SHALE.

Oct. l0, 1972 R. s. B'RI'MHALL.

METHOD 0F PROCESSING OIL SHALE Filed Feb. 16, 1970 3,697,412- Patented Oct. 10, 1972 United States Patent Oce 3,697,412 METHOD F PROCESSING OIL SHALE Ray S. Brimhall, deceased, late of Salt Lake City, Utah,

by Walker Bank and 'Irust Co., administrator, P.0.

Box 1169, Salt Lake City, Utah 84110 Filed Feb. 16, 1970, Ser. No. 11,727 Int. Cl. C10b 53/.06

U.S. Cl. 208-11 6 Claims ABSTRACT OF THE DISCLOSURE The present invention comprises a method of economically processing oil shale at W temperatures and pressures in such a manner that the effective yield of end products from kerogen in the shale is measurably increased, and at reduced cost, over that possible by the employment of conventional methods. In the present invention, the process employs the twin steps of, iirst, soaking crushed oil shale in a liquid, hydrocarbon diluent, and then, after the soaking has been completed, subjecting the shale-diluent mixture to heat to gradually increase mixture temperature from ambient condition, so as to enable maximum recovery ultimately, of distillates. The dual functions of, first, soaking the oil shale in a diluent under ambient temperature conditions and, secondly, gradually and progressively increasing the temperature of the shale, has been found to increase measurably the yield of products vaporrized from the kerogen of the shale.

The present invention relates to the processing of oil shale and, more particularly, to a new and improved, economical method of processing oil shale wherein yield is measurably increased, and at reduced production cost.

Oil shale, of course, is a sedimentary deposit containing `kerogen interspersed in mineral matter. Kerogen is a complex organic mixture which, when heated in the absence of air, becomes thermally altered, chemically, to produce shale oil in conventional, shale-retort processes; in the present invention, a broad spectrum of vapors and gasses are produced, upon uniquely raising the temperature of pre-soaked shale to enable maximum recovery of end products.

Shales vary greatly in kerogen nature and content. For a representative oil shale, crude oil resulting from pyrolysis thereof, upon distillation, will offer representative yields of from 16% to 30% naphtha, 15% to 24% light distillant, 28% to 36% heavy distillant, and 16% to 37% residuals. The naphtha cut will contain of the order of 19 to 25% paraflins and naphthenes, 43% to 60% oleiins and 21% to 36% aromatics. Various hydrocarbon gasses are given off through pyrolysis of kerogen. These gasses include methane, ethane, propane and butane. Hydrogen, hydrogen sullide, propylene, carbon monoxide, carbon dioxide and nitrogen are likewise recoverable from most shales. While kerogen is chemically complex, it is known that the same when thermally altered by pyrolsis, will cause its constituents to break down to give various hydrocarbon gasses and liquids.

Heretofore, the various techniques employed in altering the kerogen of oil shale has quite consistently involved retorting in a high temperature region. To optimize heat exchange, various techniques have been used such as steam injection, mixing heated objects such as aluminum balls and other matters with the crushed shale, firing coke end products underneath gravity-feed retorts, and so forth. Prior techniques center upon, rst, heating the shale rapidly to a high temperature to recover crude oil, and then processing the oil through conventional distillation techniques.

In the present invention, the inventor has observed an increase in yield, and a reduction in the nitrogen and sulfur content of such yield, from similar oil shale samples where, as according to the present invention, the shale in crushed form is pre-soaked in a diluent for a minimum time and then processed in a low temperature region, i.e. below 850 F. The pre-soak time should approximate ten minutes; however, preferably should not be less than seven minutes. The diluent will be a hydrogen liquid, such as a petroleum or shale oil distillant, and may comprise a stove oil cut, a diesel cut, and so forth.

Likewise essential in the practicing of this invention is a slow gradual increase, from ambient temperature conditions of the temperature of the oil shale and diluent mixture, and initial recovery of vapors in the low temperature region between, e.g. 70 F. and 350 F. It is believed that thermal alteration of the kerogen in this temperature region produces an alteration, to now unascertained chemically, which operates to increase recovery, particularly of liquid end products from the kerogen. At the same time, water content has been found to be measurably reduced.

Accordingly, a principal object of the present invention is to provide a new and improved method for processing oil shale which greatly increases percentage yield of end products.

A further object of the invention is to provide a new, economical, low pressure, low temperature method of extracting oil from shale, such oil being of reduced sulfur and nitrogen content.

An additional object of the invention is to provide a method of processing shale which will directly produce commercial end products.

An additional object of the invention is to provide a method of continuous feed in a shale processing plant so as to obtain both retorting and distillation of end products in the same plant.

In the present invention, in brief, crushed shale is provided and to which is added a hydrocarbon diluent such as a fuel cut or a stove oil cut. From laboratory tests itfis indicated that not less than 15 milliliters of diluent should be employed for every 57 grams of shale. The diluent and oil shale mixture is allowed to remain as a slurry mixture under ambient temperature conditions for approximately 10 minutes of time but in no case less than 7 minutes. After such soaking has been completed then the oil shale and diluent mixture or slurry is gradually increased as to temperature, but with vapors being maintained in intimate contact therewith and thence collected and condensed as a first fraction or first series of fractions. The oil shale, whether or not now in slurry form, is subequently passed through a series of temperature zones of progressively increasing temperatures so that successively higher 'boiling fractions may be obtained. It is noted in the process that the kerogen is not heated to extremes to produce initially a crude oil for subsequent processing as by distillation. Rather, fractional distillation is commenced at the beginning of the retort cycle of the soaked oil shale.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings in which:

FIG. l is a schematic block diagram of the method of the present invention in a preferred form thereof.

FIG. 2 is a fragmentary block diagram which may be substituted for a portion of the method flow sheet illustrated in FIG. 1.

The first step in the process of the present invention is to provide a suitable quantity of suitable oil shale for rich in organic matter and which, under generally used retort processing,-yields a shale crude oil when heated in the absence of air. While most shale sediments form oil upon distillation, the industry classifies as oil shale those sediments which produce at least 15 gals. of oil per ton. Commercial grades of oil shale will provide from 25-50 gals. per ton of shale, yto extremesof up to 150 gals-per ton.

The oil shale to be processed is next crushed. Preferably, the crushing will be such that a majority of the oil shale to be processed will pass through a 1A screen mesh. Although the process will still be operative, yet it is preferable that the particle size of the crushed oil shle is such that a majority of the same will not pass a 25 screen mesh, as sand granules may tend to settle out in the process.

The next.; step in the process is to add a hydrocarbon diluent to the crushed oil shale. The term diluent is used in its broadest sense, i.e. the amount of-crushed oil shale present in any given volume is reduced thereby, and the diluent liquid may be either reactive or non-reactive relative to the shale. In point of fact, the diluent will constitte a hydrocarbon which enjoys a liquilied state and ambient temperatures, e.g. 70 Fri-35 F. Preferably, the vdiluent vwill take the form of a bituminous distillate such asa diesel cut or stove oil. Even gasoline can be employed; howbeit, sealing problems and safety problems will be somewhat complicated thereby. While the ratio of diluent to crushed shale is not critical in practicing the present invention, optimum results are obtained where there is present at least 15 milliliters of diluent for every 57 grams of vcrushed shale.

The next step in the process is extremely important and comprises the soaking of the oil shale in the added diluent at ambient temperature for a period of time. This time is preferably of the order of minutes, which should at least be 7 minutes or more. Experimentation has indicated that the so provided soaking time is essential in preparing the shale for further processing in order that a maximum recovery may be-obtained.

The next step inthe process comprises gradually raising the temperature of the., oil shale and diluent to vaporize a first fractionin a low temperature zone. Ancillary to this step '1s to distill the so-vaporized first fraction as by confirst heating step, the same should take place such that the slurry temperature .(e.g. 50 F.70 F.) is gradually raised from ambient temperature conditions vto approximately 350 F. During this step, various gasses and vapors will be givenzoi, the nature of the same and their volume'dependng upon the type of shale being processed. Extremelyimportant in the invention is the gradual -temperature rise of the shale and diluent subsequent to the extended soak time of the prior step. It is the combination of these two steps, essentially, that increases yield in the low temperature range, e.g. below 850 F. While the exact chemistry of this phenomenon is currently unknown, yett is believed that the prior extended pre-soak plus the gradual raising of the temperatureof the so soaked oil shale, enables carbon, hydrogen and oxygen constituents..

to aid in vexpanding ,hydrocarbon chains of kerogen constituents, original or thermally modified, so that a maximumvyield can be achieved.

This iirst` step oflgradually raising the temperature of the oil shale and diluent is followed by corresponding and similar successive steps, respective ones of which are operated in progressively higher temperature regions for obtaining successive fractions. Accordingly, the second temperature rise step `may be performed in a vapor temperature region of 350 F. to 480 F., the next succeeding step from 480' F. to 560 F., and the subsequent step from 560 F. vto ,760 F. At some point in this process, subsequent to the commencement of the application of heat, it will be found that a diesel cut or stove oil` cut derived from the ascending vapors will be available for feeding back to the hydrocarbon-diluent additive step, to supply diluent to the oil shale being processed. But a small fraction of such cut need be used to be supplied the oil shale.

By the invention, either wide or narrow cuts or fractions are possible, this by regulating the temperature ranges involved and adding to or subtracting from the heat additive steps. The three dots immediately prior to the last heat application rstep indicates that any number of heat additive steps may be incorporated in the system, and with a selected hydrocarbon distillate, or a portion thereof, being re-routed back to the crushed oil shale entering the system.

Again, the key in practicing the invention resides inV its A and B method steps, in first pre-soaking the oil shale and the selected hydrocarbon diluent for a period of ap-` proximately l0 minutes, and then subsequently, gradually raising the temperature of the oil shale and diluent in stage B such that the temperature gradient does not exceed 30 F/minute. The first fraction can be obtained in a low (e.g. F. to 350 F.) temperature vapor zone.

FIG. l may be considered to be a process having both batch and continuous ow systems. FIG. 2 illustrates with particularity a continuous iiow system, wherein, at point X, the oil shale and diluent slurry is, first, advanced continuously through successively higher heat zones; then, as a subsequent step, there is separately collected and distilled vapors from respective ones of said heat zones.

As to step C, the material may be either progressively advanced over an elongate heat supply, such that as the material is advanced it progressively increases in temperature; or the separate zones themselves may be supplied with specialized heating means such that, in any event, the temperature of the shale and the temperature of the vapors rising therefrom, progressively increase, relative to respectivev successive heat zones, so that separate distillation fractions may be obtained. As to the individual heat zones, however, the vapors will be separately collected and distilled as at step D in FIG. 2 from respective ones of the heat zones, this so that different cuts may be obtained.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications maybe made without `departing from this invention in its broader aspects.

What is claimed is:

1. A method of processing oil shale at low temperatures, i.e. below 850 F., including, in-combination, providing crushed oil shale; mixing with said oil shale a hydrocarbon liquid diluent to form a mixture; soaking said oil shale in said diluent; and distilling into separate fractions said mixture by, iirst, heating said mixture in a temperature range below 850 F. toraise gradually theI temperature thereof to vaporize said mixture sufficient to form heterogeneous vapors therefrom and second, cooling said vapors to condense said vapors as separate distillates.

2. The method of claim 1 wherein, in said heating step, the temperature of said mixture is raised no greater than 30 F. for every successive minute of heat application.

3. The method of claim 1 wherein said heating step comprises heating a continuous dlow of said mixture at a series of successive heat zones of progressively lncreasing temperatures, and wherein said distilling step comprises separately ldistilling as aforesaid, in said heat zones said mixtures via vapors rising from said mixture.

4. The method of claim 1 wherein said heating step comprises progressively heating said mixture such that the temperature of said mixture passes through a series of successive heat zones of progressively increasing ternperature, said distilling step comprising separately distilling at respective ones of said heat zones said mixture via vapors rising from said mixture.

, 6 .5. The method of claim 1 wherein said heating step to form heterogeneous vapors therefrom, and cooling comprises heating said oil shale to progressively increas- Said VaPOfS t0 form Separate dlstluatesing temperature zones, said distillation step comprising separately collecting and distilling vapors ascending at suc 5 UNITED STATES PATENTS cessive ones of said zones.

6. A method of processing oil shale including, in combination, providing crushed oil shale, mixing with said oil shale a hydrocarbon liquid diluent to form a mixture, 10 CURTIS R- DAVS, Primary Examiner soaking said oil shale in said diluent a minimum of seven US. CL X'R. minutes under ambient temperature conditions, heating 201 23 said mixture to raise gradually the temperature thereof References Cited 

